This invention is directed to a reactive armor box for protecting armor surfaces on vehicles and stationary installations from projectiles, particularly so-called hollow explosive charged projectiles. More particularly, this invention is directed to a reactive armor box for protecting armor surfaces of vehicles or stationary installations wherein at least one outer surface of the box has radar absorbing characteristics for absorbing radio waves of the radar to avoid detection of the protected armor surface and to protect said armor surface from projectiles utilizing radio frequency guidance seekers, and semiactive R.F. guidance systems.
A reactive armor box for protecting armor utilizing two or more explosive cassettes against the destructive force of projectiles including hollow explosive charge projectiles is well known. One such system or arrangement is disclosed in U.S. Pat. No. 4,368,660, issued Jan. 18, 1983, for "Protective Arrangement Against Projectiles, Particularly Hollow Explosive Charge Projectiles" to Manfred Held. The patentee states that his invention relates to a protective arrangement against projectiles where a wall structure is formed from a wall layer of explosive material, and at least one additional wall layer covering at least one face of the wall layer of explosive material. The additional wall layer is said to be a non-explosive, inert high-density material such as metal. The patentee states that in one embodiment both faces of the explosive wall layer are covered with a layer of inert, non-explosive high-density material such as metal. The protective arrangement is said to be particularly suitable for protection against the destructive force of hollow explosive charge projectiles.
Such protective arrangements are well known in the above identified art but have significant drawbacks. One significant drawback for such boxes or protective devices is that such armor boxes are generally very heavy and are constructed of dense metal material such as steel, and are consequently very heavy and difficult to handle. At times, such armor boxes must be removed from the surfaces which they protect and this heavy weight makes this difficult.
The reactive armor box is generally mounted on an armored surface at an angle to the attack of any jet shot line. When the jet shot line intercepts the first cassette, the explosive is ignited due to the impact forces of the jet shot line. This explosion detonates the metal plates which intercept the jet shot line at an angle, thereby further disrupting the jet shot line. The second cassette acts in the same manner to further weaken or deflect the jet shot line. The lateral strength of shaped charge jets is weak and even with the tip of the jet travelling at velocities up to 10,000 mps and the aft or rear portion of the jet travelling at 3,000 mps, such plates have proven to disrupt the jet shot line. Such boxes are typically mounted over thick armor such as Rolled Homogeneous Armor, ceramics, spaced angled steels, or other passive armor. Once the jet has been disrupted by the flying plates and the explosive charge, the passive armor will stop the remaining penetrator.
On the other hand, kinetic energy penetrators (typically long metal rods) are stronger in the lateral direction. Long rod kinetic energy penetrators are usually on the order of 1000 mm long with a diameter of 12 to 20 mm. The cassettes are not as effective against this type of penetrator, or, at least, the cassettes designed to interrupt shaped charge jets are not found to be as effective. The kinetic energy rod travels at a much lower velocity of 1,525 to 2,067 mps; consequently, by adjusting the size of the cassettes and the amount of explosive force contained therein to control its velocity, it is possible to optimize the reactive armor against this more formidable threat.
Armor effectiveness is measured by its ability to defeat the threat as a function of areal density or Kg/m.sup.2. The steel design prior art box typically weighs 5.75 Kg and has an areal density of 146 Kg/m.sup.2. This excessive weight makes the prior art armor boxes difficult to handle and adds to the weight of the vehicle to which they are added.
The steel design used in the prior art devices have the further drawback of readily reflecting radar or radio waves permitting the ready detection of the protective surface by radar and the use of terminal guided weapons or projectiles that use radio frequency guidances, such as 35 GHz and 94 GHz seekers, thereby making the protected armor surface susceptible to such homing missiles or projectiles.